Background: Mitomycin C is used in pterygium surgery for the prevention of recurrence of pterygium. Mitomycin C has a long-lasting effect and serious complications have been reported. Purpose: This report describes two patients who experienced severe early and late complications associated with the use of mitomycin C after pterygium surgery that required surgical intervention. Patients and methods: Case 1: A 66 year old man underwent bare sclera pterygium excision, with intraoperative 3 minute application of 0.02% mitomycin C. Three weeks postoperatively the patient presented with Pseudomonas aeruginosa scleritis with corneoscleral melting and perforation. Topical and systemic antibiotics were administered, and the perforation was closed using corneal lamellar graft. The eye developed choroidal and exudative retinal detachment, which resolved after 2 months, and a dense cataract that was extracted by phacoemulsification. Case 2: A 58 year old woman underwent bare sclera pterygium excision, followed by instillation of 0.02% mitomycin drops twice daily for 5 days. For 6 years, the patient experienced incapacitating photophobia and pain. A conjunctival defect with calcium deposits and irregular corneal epithelium were unresponsive to medical treatment and tarsorrhaphy. A limbal conjunctival autograft from the fellow eye was performed. The corneal and conjunctival epithelium healed, and the patientís discomfort improved markedly. Results: Lamellar corneal graft and conjunctival-limbal autograft have been used sucssesfully to reconstruct scleral melting and ocular surface problems associated with mitomycin C application. Conclusions: Mitomycin C should be used cautiously due to the associated risk for severe complications.